This invention relates to a method of operating a telecommunications system comprising a switching facility and subscriber channels over which data are transmissible in packet form.
Such a telecommunications system is, for example, an ISDN system, which transmits both voice and data in digital form from one subscriber over 64-kb/s channels, called “B channels”, to another subscriber.
The invention is applicable to the transmission of data of the subscriber if these data are offered in packet form, i.e., as a sequence of packets, on the subscriber's access channel (B channel). As is well known, these packets include destination address information of a general kind (i.e., not necessarily the telephone number of the desired subscriber).
The invention is applicable to voice transmission if the subscriber terminal itself converts voice information into packet form, as is done for voice transmission over the Internet.
Prior-art telecommunications systems with a switching facility are normally dimensioned so that not all subscribers can establish a call to the switching facility and to other subscribers at the same time, but the capacity of the switching facility in terms of channels that can be switched simultaneously is less than the number of subscribers connected. During data transmission, particularly if the duration of the respective data call is long compared to the duration of usual telephone calls, this may result in access to the switching facility being temporarily impossible because all channels leading to the switching network of the switching facility or all outgoing channels are busy.